Modified Cut-Off Value of the Urine Protein-To-Creatinine Ratio Is Helpful for Identifying Patients at High Risk for Chronic Kidney Disease: Validation of the Revised Japanese Guideline

Modified Cut-Off Value of the Urine Protein-To-Creatinine Ratio Is Helpful for Identifying Patients at High Risk for Chronic Kidney Disease: Validation of the Revised Japanese Guideline

HIROYUKI YAMAMOTO,^1,2 KYOKO YAMAMOTO,^1,3,4 KATSUMI YOSHIDA,⁵ CHIYOHIKO SHINDOH,³ KYOKO TAKEDA,⁶ MASAMI MONDEN,⁷ HIROKO IZUMO,⁷ HIROYUKI NIINUMA,⁸ YUTARO NISHI,⁸ KOICHIRO NIWA8 AND YASUHIRO KOMATSU¹

¹Division of Nephrology, Department of Internal Medicine, St. Luke's International Hospital, Tokyo, Japan
²Oiwa Nephrology and Dialysis Clinic, Tokyo, Japan
³Department of Laboratory Medicine and Clinical Science, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
⁴Department of Thoracic Medical Oncology, Cancer Institute Hospital of Japanese Foundation for Cancer Research, Tokyo, Japan
⁵Healthy Medical Center, Tohoku Kosai Hospital, Sendai, Miyagi, Japan
⁶Clinical Laboratory Department, St. Luke's International Hospital, Tokyo, Japan
⁷Division of Endocrinology and Metabolism, Department of Internal Medicine, St. Luke's International Hospital, Tokyo, Japan
⁸Department of Cardiology, Cardiovascular Center, St. Luke's International Hospital, Tokyo, Japan

Chronic kidney disease (CKD) is a global public health issue, and strategies for its early detection and intervention are imperative. The latest Japanese CKD guideline recommends that patients without diabetes should be classified using the urine protein-to-creatinine ratio (PCR) instead of the urine albumin-to-creatinine ratio (ACR); however, no validation studies are available. This study aimed to validate the PCR-based CKD risk classification compared with the ACR-based classification and to explore more accurate classification methods. We analyzed two previously reported datasets that included diabetic and/or cardiovascular patients who were classified into early CKD stages. In total, 860 patients (131 diabetic patients and 729 cardiovascular patients, including 193 diabetic patients) were enrolled. We assessed the CKD risk classification of each patient according to the estimated glomerular filtration rate and the ACR-based or PCR-based classification. The use of the cut-off value recommended in the current guideline (PCR 0.15 g/g creatinine) resulted in risk misclassification rates of 26.0% and 16.6% for the two datasets. The misclassification was primarily caused by underestimation. Moderate to substantial agreement between each classification was achieved: Cohen's kappa, 0.56 (95% confidence interval, 0.45-0.69) and 0.72 (0.67-0.76) in each dataset, respectively. To improve the accuracy, we tested various candidate PCR cut-off values, showing that a PCR cut-off value of 0.08-0.10 g/g creatinine resulted in improvement in the misclassification rates and kappa values. Modification of the PCR cut-off value would improve its efficacy to identify high-risk populations who will benefit from early intervention.

keywords —— chronic kidney disease; Cohen's kappa statistic; urine albumin-to-creatinine ratio; urine protein-to-creatinine ratio; validation

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Tohoku J. Exp. Med., 2015, 237, 201-207

Correspondence: Hiroyuki Yamamoto, M.D., Ph.D., MPH, Division of Nephrology, Department of Internal Medicine, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.

e-mail: yama-h@umin.ac.jp

Yasuhiro Komatsu, M.D., Ph.D., MPH, Division of Nephrology, Department of Internal Medicine, St. Luke's International Hospital, 9-1 Akashi-cho, Chuo-ku, Tokyo 104-8560, Japan.

e-mail: komayasu@luke.ac.jp